急倾斜煤层群水力增透防突技术研究与应用

发布时间：2018-08-26 21:09

【摘要】：煤矿瓦斯灾害一直以来都是威胁煤矿井下安全的第一杀手。根据相关统计数据,自1949年以来,瓦斯灾害导致百人身亡的灾难性事件多达20余起。纵观建国以来的煤矿安全史,瓦斯灾害及瓦斯灾害诱发的重大及特别重大煤矿安全事故时有发生,瓦斯灾害事故尚未得到彻底的根治。为了有效防治瓦斯事故,煤与瓦斯突出灾害防治理论、技术和工程历来都是国家科技重大研究领域的热点。我国煤炭资源量大,但其透气性普遍很低。据有关部门统计,我国93.4%的煤矿可采的是松软煤层,其透气性系数大都小于0.05mD,故而在生产过程中发生瓦斯事故的可能性非常高。近年来,随着“先抽后采”政策的应用以及技术的逐渐成熟,在获得煤炭、煤层气两种能源的同时,对于瓦斯的治理又出现了新的问题,那就是寻找一种在瓦斯含量高,但透气性低的煤层中既能扩大瓦斯抽采范围,又能提高瓦斯抽采率的方法。重庆市中梁山矿区煤层瓦斯含量高、透气性低、煤层f值较低,且煤层为近距离急倾斜薄煤层群,使得其瓦斯抽采难度较大,技术要求较高。本文以中梁山南矿为研究对象,对其煤层的瓦斯赋存条件以及现有抽采方案进行深入分析,同时本着提高瓦斯抽采量、减小瓦斯突出事故风险的原则,展开了快速高效瓦斯抽采理论、技术及设备的研究以及工程应用工作,在水力增透瓦斯抽采技术、装备及工程应用方面取得了创新成果,亦成为本论文核心研究成果。本论文的创新点主要在于借助高压水的动力效应(气蚀、振动、冲击等)诱发煤层应力场及矿岩裂隙发育的动态进程,加速提高高瓦斯煤层的裂隙发育,增大煤层透气性,进而为煤层瓦斯抽采创造有利条件;结合中梁山南矿瓦斯灾害防治工程实践,系统开展了高压水射流割缝与水力压裂在近距离、急倾斜、低透气性薄煤层群中的动力效应及瓦斯灾害控制技术研究;通过理论分析与数值模拟两种方法,推演了高压水射流割裂技术的作用方式,分析水压作用下煤体中的固、液、气三相耦合特性,研究应力场与裂隙场的动态演化规律,从而确定了高压水射流割裂、水力压裂的动力效应以及煤层中的瓦斯运移规律与其透气性之间的动态关系;通过对透气性较差的煤层中的高压水射流割裂技术与水力压裂卸压增透技术的研究,从而实现瓦斯抽采及灾害防治技术成功地应用在中梁山南矿瓦斯灾害防治工程中。论文的主要研究成果如下:一、定向水力压裂机理研究在测定中梁山南矿煤体基本参数的基础上,分析了高压水对煤层的压力致裂机理,揭示了煤层卸压增透的动力学效应。首先明确了水力压裂中钻孔起裂对压裂裂隙控制设计的重要性,而后以此为依据,按照钻孔注水压裂过程的两个主要步骤(钻孔、注水)分别分析了钻孔后的围岩体的应力分布形态,再根据煤体中布置的注水压力孔的不同位置,阐明了考虑煤层厚度和钻孔偏差角情况下的穿层钻孔的起裂原理。二、高压水射流割缝增透原理研究通过采集中梁山南矿煤样,并测定其物理力学特性,结合流体力学、损伤力学等理论基础,分析了中梁山南矿通过采用高压水射流割缝增透的方法提高抽采效率的作用原理:煤体在高压水射流作用下产生割缝,同时发生拉压变形以及剪切变形,使得煤体产生损伤破坏,导致原本存在于煤体中的裂隙发生扩张现象,同时又使煤体产生新的破坏裂隙,降低了地应力,从而既提高煤体的透气性系数,又增大了煤体的暴露面积,有利于吸附在煤体上的瓦斯发生解吸,变为游离态的瓦斯,提高了煤层瓦斯的抽采效率。三、高压水射流割缝关键参数与瓦斯抽采效果研究在测定中梁山南矿煤体基本参数的基础上,合理分析了高压水射流割缝水力参数,根据crow切割理论,对影响水射流切缝深度的主要因素进行了深入的分析,主要有两个:其一,水力参数(包括射流压力和喷嘴直径),其二,切割条件(包括喷嘴横移速度和重复切割次数)。通过理论分析瓦斯预抽孔有效抽采半径的影响因素,确定了有效抽采半径的试验方法,并在中梁山南矿进行了高压水射流割缝后钻孔抽采半径考察试验,现场考察的结果表明:在25mpa割缝压力下,计算出压水射流割缝半径可达1.57m,自然排放半径可达4.58m,瓦斯抽采有效半径可达9.14m,瓦斯极限抽采时间约为10个月,在误差允许范围内和现场考察结果基本一致。四、水力增透技术的现场试验研究与工程管理创新在分析了高压水对煤层的压力致裂机理基础上,将水力压裂技术及中梁山现有的压裂设备能够应用于中梁山低透气突出煤层的瓦斯抽采。压裂效果表明:采用brw31.5/200型乳化泵在泵压24~27mpa,40min~70min的条件下压裂范围可达15m~25m;采用bzw-200/50型乳化泵泵压35mpa~40mpa,80min~100min条件下压裂范围可达70m~100m。水力压裂技术能够适用于中梁山的煤层,并能取得的较好的抽采效果。进行定向水力压裂试验后,瓦斯预抽孔终孔间距增加了1倍,大幅减少了钻孔工程量,平均单孔瓦斯抽放纯量提高了925%;平均抽采浓度提高了80%,且能进行长时间的瓦斯抽采。每次压裂过程中,乳化泵都处于满流量负荷状态,每次压裂注入水量差异不大,南矿最大压裂半径达到70m,而北矿最小压裂半径仅为10m,中梁山南矿的压裂效果明显比北矿好。通过比较分析南、北矿压裂试验区域地质条件可知,南矿试验区域地质条件相对较好,试验区域内断层、裂隙较少,煤层起裂之后能沿着导向缝槽延展,注入水量流失较少。因此,在选择压裂区域时,应首选地质条件较好的区域。中梁山现有的压裂设备(BZW200/50乳化泵、KJR19×6S-63MPa高压管、高压流量表等)、封孔工艺等基本满足现有的压裂需求。在测定中梁山南矿煤体基本参数的基础上,开发出适用于中梁山矿区的高压水射流割缝工艺。现场工程应用表明:中梁山南矿140NEC4-C5抽采巷,高压水射流割缝孔累计抽采瓦斯量原始钻孔的4.41倍,高压水射流割缝孔平均标准抽采纯量为原始钻孔的4.2倍,达到预期抽采纯量提高50%的目标。中梁山北矿70NEC3和南矿-20NWC0石门钻场,应用高压水射流辅助石门揭煤后,钻孔数量减少40%以上。对比中梁山南矿、北矿水力压裂效果及实验区域煤层地质条件分析得出,对于地质条件较差的区域,主要采取高压水射流割缝进行卸压增透,为今后开展急倾斜、近距离煤层群水力化工程措施总结了经验。按照国家相关的瓦斯抽采方针政策与规范,结合中梁山矿多年来的抽采实际工程经验,本论文总结并全面实施了适合急倾斜近距离薄煤层群的瓦斯抽采工程管理模式,即“密钻孔,严密封,综合抽,长期抽”十二字措施。五、瓦斯突出矿井防突预警技术与管理保障机制建立了中梁山南矿煤与瓦斯突出预警指标体系及预警模型,定制开发了系列专业软件系统,构建了中梁山南矿煤与瓦斯突出实时诊断与预警系统,并建立了预警系统运行保障机制。从而,实现了防突信息的自动化管理,突出灾害的实时监测、在线分析、智能预警,以及突出预警信息的局域网综合管理、即时发布与实时共享,达到煤与瓦斯突出危险性智能预警、辅助决策的目标,提高了矿井安全技术和防突管理水平。
[Abstract]:Coal mine gas disaster has always been the first killer to threaten the safety of coal mine. According to relevant statistical data, since 1949, gas disaster has caused more than 20 catastrophic incidents in which 100 people have died. Throughout the history of coal mine safety since the founding of the People's Republic of China, major and especially major coal mine safety accidents caused by gas disaster and gas disaster have occurred from time to time. In order to effectively prevent and control gas accidents, the theory, technology and engineering of coal and gas outburst disaster prevention and control have always been a hot topic in the major research fields of national science and technology. In soft coal seam, the permeability coefficient is mostly less than 0.05 mD, so the possibility of gas accidents in production process is very high. In recent years, with the application of the policy of "pumping first and then mining later" and the gradual maturity of technology, new problems have arisen in the control of gas while acquiring coal and coal-bed methane, that is to find one. The method of enlarging gas extraction range and increasing gas extraction rate can be used in coal seams with high gas content but low permeability. The coal seams in Zhongliangshan mining area of Chongqing have high gas content, low gas permeability, low F value of coal seams, and the coal seams are short distance steeply inclined thin seams, which make gas extraction more difficult and require higher technology. Taking Zhongliangshan South Coal Mine as the research object, this paper makes a deep analysis of the gas occurrence conditions and the existing gas extraction schemes in its coal seam. At the same time, in accordance with the principle of increasing the gas extraction capacity and reducing the risk of gas outburst accidents, the theory, technology and equipment of rapid and efficient gas extraction as well as the engineering application work are carried out. Innovative achievements have been made in technology, equipment and engineering applications, which have become the core research results of this paper. The innovation of this paper is mainly to accelerate the development of high gas seam fractures and increase the permeability of coal seam by means of the dynamic effects of high pressure water (cavitation, vibration, impact, etc.) to induce the stress field of coal seam and the dynamic process of fracture development of ore and rock. Combining with the practice of gas disaster prevention and control engineering in Zhongliangshan South Coal Mine, the dynamic effect and gas disaster control technology of high pressure water jet slotting and hydraulic fracturing in thin coal seams with short distance, steep inclination and low permeability are studied systematically. The method deduces the action mode of high pressure water jet fracturing technology, analyzes the coupling characteristics of solid, liquid and gas in coal under the action of water pressure, studies the dynamic evolution law of stress field and fracture field, thus determines the dynamic effect of high pressure water jet fracturing, hydraulic fracturing and the dynamic relationship between gas migration law and gas permeability in coal seam. Through the study of high pressure water jet cutting technology and hydraulic fracturing pressure relief and permeability enhancement technology in coal seams with poor permeability, the gas extraction and disaster prevention technology has been successfully applied to the gas disaster prevention and control project in Zhongliangshan South Coal Mine. Based on the basic parameters of coal body in Zhongliangshan South Coal Mine, the pressure fracturing mechanism of high pressure water to coal seam is analyzed, and the dynamic effect of pressure relief and permeability enhancement is revealed. The stress distribution pattern of the surrounding rock mass after drilling is analyzed separately, and then according to the different positions of the injection pressure holes arranged in the coal body, the initiation principle of the cross-layer drilling considering the thickness of the coal seam and the deviation angle of the borehole is expounded. 2. The principle of high-pressure water jet cutting seam penetration is studied by collecting coal samples from Zhongliangshan South Coal Mine and measuring them. Based on the physical and mechanical characteristics and the theory of fluid mechanics and damage mechanics, this paper analyzes the principle of improving extraction efficiency by using high pressure water jet slotting method in Zhongliangshan South Coal Mine. It leads to the expansion of the cracks existing in the coal body, and at the same time causes the coal body to produce new destructive cracks, reducing the ground stress, thus not only improving the permeability coefficient of the coal body, but also increasing the exposed area of the coal body, which is conducive to the desorption of the gas adsorbed on the coal body, turning into free gas, and improving the extraction of coal bed gas. Third, on the basis of measuring the basic parameters of coal body in Liangshan South Coal Mine, the hydraulic parameters of high-pressure water jet slotting are reasonably analyzed. According to crow cutting theory, the main factors affecting the depth of water jet slotting are analyzed in depth. There are two main factors: first, hydraulic parameters. Parameters (including jet pressure and nozzle diameter), secondly, cutting conditions (including nozzle transverse velocity and repeated cutting times). Through theoretical analysis of the factors affecting the effective radius of gas pre-drainage hole, the test method of effective radius of gas pre-drainage was determined, and the radius of borehole extraction after high-pressure water jet cutting was investigated in Zhongliangshan South Coal Mine. The results of field investigation show that the cutting radius of pressurized water jet can reach 1.57 m, the natural discharge radius can reach 4.58 m, the effective radius of gas extraction can reach 9.14 m, the limit time of gas extraction is about 10 months, and the results of field investigation are basically consistent within the allowable error range. Based on the analysis of pressure fracturing mechanism of high pressure water to coal seam, hydraulic fracturing technology and existing fracturing equipment of Zhongliangshan can be applied to gas extraction in Zhongliangshan low permeability outburst coal seam. The range of fracturing can reach 15-25 m, the range of fracturing can reach 70 M-100 m under the condition of 35 mpa-40 MPa pump pressure of bzw-200/50 emulsifying pump and 80 min-100 min pressure. Hydraulic fracturing technology can be applied to Zhongliangshan coal seam, and can achieve good pumping effect. After directional hydraulic fracturing test, the distance between gas pre-drainage holes and final holes is doubled and greatly reduced. In each fracturing process, the emulsified pump is in the state of full flow load, and the injection water volume is little different. The maximum fracturing radius in the South Mine is 70m, while the minimum fracturing radius in the North Mine is only 10m. The fracturing effect of Zhongliangshan South Coal Mine is obviously better than that of the North Coal Mine.Through comparative analysis of the geological conditions of the South and North Coal Mine fracturing test areas,it can be seen that the geological conditions of the South Coal Mine test areas are relatively good,the faults and fractures in the test areas are few,the coal seams can extend along the guide slot after initiation of fracture,and the amount of injected water loss is less.Therefore,the fracturing area should be selected. The existing fracturing equipment (BZW200/50 emulsifying pump, KJR19 *6S-63MPa high pressure pipe, high pressure flowmeter, etc.) and sealing technology basically meet the existing fracturing requirements. Based on the determination of the basic parameters of coal body in Zhongliangshan South Mine, the high pressure water jet cutting technology suitable for Zhongliangshan Mine is developed. The field application shows that: in the 140NEC4-C5 suction roadway of Zhongliangshan South Coal Mine, the cumulative gas drainage by high pressure water jet slotting hole is 4.41 times of the original borehole, and the average standard gas drainage by high pressure water jet slotting hole is 4.2 times of the original borehole, reaching the target of 50% increase of the expected extraction purity. Compared with Zhongliangshan South Coal Mine, the effect of hydraulic fracturing in North Coal Mine and the geological conditions of coal seams in the experimental area, it is concluded that in the areas with poor geological conditions, high-pressure water jet slotting is mainly adopted to relieve pressure and increase permeability, so as to carry out steep inclination in the future and hydraulize the coal seams at short distance. According to the relevant national gas drainage policy and norms, combined with the actual engineering experience of Zhongliangshan Coal Mine for many years, this paper summarizes and fully implements the management mode of gas drainage engineering suitable for steeply inclined close-range thin seam group, namely "tight drilling, tight sealing, comprehensive drainage, long-term drainage". Fifthly, the early warning technology and management guarantee mechanism of coal and gas outburst prevention in Zhongliangshan South Coal Mine have been established. The early warning index system and early warning model of coal and gas outburst have been established. A series of professional software systems have been customized and developed. The real-time diagnosis and early warning system of coal and gas outburst in Zhongliangshan South Coal Mine has been established, and the operation guarantee mechanism of the early Thus, automatic management of outburst prevention information, real-time monitoring of outburst disasters, on-line analysis, intelligent early warning, and integrated management of outburst early warning information by LAN are realized, which can be issued and shared in real time. The goal of intelligent early warning of coal and gas outburst danger and assistant decision-making are achieved, and the level of mine safety technology and outburst prevention management is improved.
【学位授予单位】：中国矿业大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TD713.3

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